The present invention relates to generator systems, and more particularly to mechanical couplings for generator systems.
Gas turbine engines, such as those used for aerospace applications, often power a generator that generates electricity. The generator used for aerospace applications is typically mounted to an accessory gearbox, which is in turn mechanically coupled to a driven shaft of the gas turbine engine. For most aerospace applications, the generator is configured to allow disconnection from the driven shaft of the gas turbine engine, which provides safety benefits.
A typical prior art generator system includes a generator rotor and generator stator, a drive shaft engaged with the generator rotor, and an input shaft. In this configuration, the input shaft is a part of the generator assembly, such that removal of the generator from the accessory gearbox removes the input shaft along with all the other generator components. The generator rotor is supported by first and second sets of bearings, and the drive shaft is splined to the generator rotor. The input shaft is supported by a third bearing. One end of the input shaft is normally engaged with the drive shaft, but can be disengaged from the drive shaft by a clutch in order to disengage the generator. Another end of the input shaft is splined for engagement with the accessory gearbox, which provides a rotational input to power the generator. When the input shaft is disengaged from the drive shaft by the clutch, the input shaft remains engaged to and powered by the accessory gearbox, which causes rotation of the third set of bearings. The third bearing is sealed within the generator.
In the prior art configuration described above, oil scavenging and supply is generally provided within the generator. Upon disengagement of the drive shaft by the clutch, oil scavenging and supply within the generator ceases. This generally presents little concern to most components of the generator, as the generator is not operating to generate electricity and components like the first and second sets of bearings do not experience rotation. However, when the generator is disengaged by the clutch, the third set of bearings and the input shaft will continue to rotate, but will generally lack lubrication. This requires special design of the third set of bearings to permit operation without lubrication for a suitable length of time.
It is desired to provide a generator system with a mechanical coupling that reduces or eliminates design constraints for operation of the generator without lubrication.